The invention relates to a technique for using a specially processed sugar cane ash in drilling fluids and using sugar cane ash with other ingredients to control filtration, wherein the additive does not increases the viscosity of the drilling fluid by more than 10%.
A need has long existed for an environmental-friendly additive for drilling fluids that does not cause the drilling fluid to become thick and viscous.
In the process of drilling oil and gas wells, porous formations are encountered. These formations allow for either whole drilling fluid or filtrate from the drilling fluid to enter the formation. After the fluid enters the formation, a thick layer of solids are deposited along the wellbore acting as a filter. This thick layer of solids, in most instances, causes the drill pipe to become stuck in the wellbore, preventing any further drilling.
The invention relates to compositions for use in well-working operations such as drilling, workover and completion, packing and the like, well-working processes utilizing such compositions, and an additive to assist in filtration control of matter into the formation, creating a more “environmental-friendly” drilling operation.
In the drilling of wells for oil and gas, drilling fluids (“drilling muds”) are circulated in such a manner as to remove cuttings and to support the walls of the hole. The fluids may be either (a) water based, comprising for example, clay, polymers, and other additives dispersed in water, or (b) oil based, comprising for example, suspending agents (generally organophilic clays), emulsifiers, stability agents, filtration control agents, weighting agents, and other additives dispersed in a medium, like diesel oil and similar oleaginous mediums.
A thin, low-permeability filter of some form is desired on the sides of the borehole to control the filtration characteristics of the drilling fluid since the pressure of the mud column in the borehole is greater than the formation pressure. A filter forms when the drilling fluid contains particles of a size only slightly larger than the size of the pore openings of the formation. The liquid, which enters the formation while the filter layer is being established, is known as the surge loss or spurt loss. The liquid that enters after the filter layer is formed is known as the drilling fluid filtrate. The permeability of the filter layer is directly related to the particle size distribution in the drilling fluid, and, in general, the filter layer permeability decreases as the concentration of particles in the colloidal size range increases.
The amount of potential filtration from a well depends on the nature of the formations being drilled and on the type of drilling fluid used. Thus, in water-sensitive formations, oil-based mud provides superior filter characteristics when the salinity of the aqueous phase of the mud is adjusted to prevent damage to the formation.
The filtration rate must be controlled when penetrating potentially productive formations in order to minimize any damaging effects from fluids entering the formation. It has been desired to have low cost filtering materials for drilling muds.
When the drilling bit passes through the porous or fractured strata, the hydrostatic pressure caused by the vertical column of drilling fluid can easily exceed the ability of the surrounding earth formation to support this pressure. Consequently, drilling fluid is lost to the formation and fails to return to the surface. This loss may be any fraction up to 100% loss of the total circulating drilling fluid volume. This condition is known in the art as “lost circulation”. Even with the best drilling practices, circulation losses can and will occur. Loss zones can be classified as filtration loss, partial loss, or complete loss.
A need has existed to control filtration losses for formations using very fine particles in the mud to provide a filter in the wellbore.
In the rotary drilling of wells with aqueous base drilling fluids, various problems associated with viscosity of the drilling fluid may occur, such as slow drilling rate, excessive drill pipe torque and drag, differential sticking, etc. See for example U.S. Pat. No. 4,356,096, incorporated herein by reference. This patent discloses that liquid-lubricating additives can be adsorbed onto certain hydrophobic, organophilic, absorbents to filter out or deposit in the wall layer on the sides of the borehole. This results in an increased concentration of the liquid lubricant in the wall layer where it is needed. The liquid lubricant can be premixed with the adsorbent before adding the resulting solid lubricating additive to the drilling fluid.
It is object of the present invention to provide an additive that is very effective as a filtration in both water-based and oil-based well-working fluids, that work as a filter and has no harmful environmental side effects.
It is another object of this invention to provide well-working compositions having a filtration control coupled with a “green” or positive environmental benefit.
Still another object of this invention is to provide a method of filtration control for water-based and oil-based well-working fluids using an organic particulate that has been carbonized.
These and other objects of the invention will appear to one skilled in the art as the description thereof proceeds.